Piano pin block



Patented Jan. 25, 1944 PIANO PIN' BLOCK Paull Bilhuber, Douglas Manor,N.`Y., assgnor to SteinWay-& Sons, New Y0rk,`N. Y., acorporation of'NewYork Application August 7, 1943, Serial No."497,770

(CLM-F188) 2 `Claims.

'i This invention relates to piano pnblocks and has for its object toprovide an `improved pinblock which will cooperate with the string frameina manner as if both string frame and'pinblock were one piece and inwhich the pinblock is protected against moisture and warping andloosening of tuning pins. The invention is also 'for the process ofmaking the same.

'The invention simplifies the manufacturing of pinblock and string framejoining, and thus reduces cost.

v-Inthe making of such pinblocks, the wood of the pinblocks is removedby planing, carving and scraping or both, to bring the excess thicknessof the top surface ofthe pinblock and one side thereof down to the leveland shape or conformation of that part f the plate that is adjacent tothe pinblock. After much trial and error on the pinblock it is nallyfitted to the string frame, but at the best a true t is not obtained,and the spaces or voids between the string frame and -pinblock aresubject to the entrance of moisture and air, and oxidation sets in tothe injury of the proper registration or fit of the two members,

`f which also brings about the loosening of the tuningV pins. Also, theloosening of the tuning pins is due to change in moisture content of thewood of the pinblock when under or subject to atmospheric changes. Suchconditions also cause string tensions and their concomitant loss ofpitch in both the unisons of a tri-chord or bi-chord note, as well' askindividual notes in the piano scale or group of notes that will causethe piano to be out of tune.

The invention consists of an improvedcombined pinblock and string plate,having its adja- 1 cent surfaces fitted by an intermediate layerofmaterial, initially plastic and then hardenedand joining the layer tothe pinblock so as'to be one pitch therewith, to receive on its uppersurface which is in intaglio with the lower surface of the string frameand in complete registration therewith, the said string frame, so thatthe pinblock and string frame form substantially one'piece though notphysically joined, no voids or spaces being between the same throughouttheir contiguous surfaces.

The invention also contemplates the treatment of the wooden pinblock toremove moisture therefrom. The invention also contemplates coating theexposed portions with a water proofing to retain the dryness of thesame.

' The invention will be further described in connection with theembodimentshown in the drawing and willfbe finally pointed out inthefclaims.

Figure 2 is a transverse section on line 2-2of VFig. 1;

. Figure 3 is a section of the improved pinblock with a filler layerwithout'the string plate being applied thereto;

Figure 4 is a section with the string plate applied to the ller before'pressure is applied; and

Figure 5 is a section of the improved combined pinblock and stringplate,` provided with a hermetically sealed coating.

Similar characters of'reference' indicate corresponding parts throughoutthe various views.

Referring to the drawing, and more particularly to Figurev 1, thepinblock I0 has applied thereto the string'plate l I, which is providedwith tuning pins l2, for the stringsIS. A string 'plate with pins iswell knownv both in grand'and upright pianos, and such string plates onthe side opposite to the side from which the pins project, rest upon aWooden beam. i5, extending across the front of a grand piano or acrossthe top of an upright piano. Asknown, the front of the beam l5 has gluedthereto an angle piece M called case corner or bar front in grandpianos.

' of 'ply construction.

.The upper and lateral surfaces Ia and |512 of the pinblock I0, inaccordance with'the invention, are slightly less in height and less inwidth by aboutk onek sixteenth of an inch, in respect to the pinblockheretofore used. While the reducedpin.- block is planed on its surfacesI5a and 15b, nevertheless the surfaces are not actually smooth, sinceunder the microscope hills and depressions would appear as alsomolecular angularities. In consequence, when the surface i la is placedupon the surface 15a. and the surface l lb upon the surface |512;instead of being truly parallel, spaces i or voids are lefttherebetween, which are irregular in size and depth due to theirregularities of the'contiguous surfaces. Even when` considerable` timeis spent fitting the surfaces l5a and |527 to match the surfaces Ila andHb, spaces or voids will nevertheless remain, as there is no-accuratemethod known by which such spaces or voidscan Vbe detected and thenremoved and a perfect ht 4commercially possible is nevertheless subjectto 'the objections above pointed out.

In accordance with the invention, in order to remove any and all spacesand voids, the surfaces ld and |527, are provided with a layer 20 of afiller material of about three thirty-seconds inches in depth, and thislayer is trowelled to provide reasonably smooth outer surfaces, and tohave the filler layer of substantially even depth.

'I'his filler is a water soluble resin paste of the urea formaldehyde orsimilar type with an admixture of wood flour 20% to 30% by weight, thewood flour having a sieve value of about 80 to 100. 'I'he proportion ofcatalyst to the formaldehyde and wood flour, is such that a hardening ofthe mix takes place at room temperature or at temperature higher thanroom temperature.

Before hardening of the mix and shortly after the filler layer has beensmoothed, the string plate is applied and pressed thereupon. It isallowed to remain a shorttime to permanentize the impressions of thelower surfaces f the string frame upon the plastic filler layer, when'the string frame is removed. Thus, the'string frame acts as a male dieto duplicate its configuration upon the plastic filler layer'throughoutboth the surfaces of the filler layer and the surfaces of the stringframe. Such pressing of the string frame upon the filler layer removesall possibility of voids and spaces between the pinblock. Removal of thestring frame from the pinblock leaves the exact reverse contour of theplate surface in the nature of an intaglio or seal impression. Theexcess material is squeezed out t0 the front, sides and bottom, and toprevent this excess from entering the tuning pin openings of the plate,a thin cloth is placed between the surface I la and the top of thefiller layer, these holes having been drilled into the plate beforehand.

To hasten the drying and curing of the ller layer which at roomtemperature would take place in about three to ve hours, depending onthe amount of catalyst used as a hardener, use is made of anelectrostatic field of high frequency current to heat the filler and thepinblock.

The layer coated pinblock is placed between two copper sheet electrodesand the moisture is driven out of the layer, and the resin is cured andconverted and hardened in accordance with a greatly accelerated rate. Atthe same time drying and dispersing of the moisture in the pinblock isintended to be carried out. Instead thereof, stray-field electrostaticheating with a grid type electrode brought near the surface to be curedmay be used. A temperature rise of 100 F. above room temperature issuiiicient to permanently set the layer in or 20 minutes at frequenciesof 2 to 4 megacycles in a voltage range of 3000 to 5000. Under suchtreatment, the filler layer fully hardens and retains the exactimpression left by the surfaces of the string frame and results in apermanence of it, a waterproofing layer and a considerable reduction ofthe curing time.

When cured a layer or film of this material is waterproof andeffectively seals the pores of the wood against penetration of moistureunder changing climatic conditions. Due to the registration of pinblockand string plate, moisture is excluded therebetween. The remainingsurfaces not covered by the filler layer are then covered with a resinfinish or moisture resistant coating of Ian oil varnish type preventingmoisture gain or loss and inhibiting warping, checking and distortion ofthe wood and preserving thereby the grip or friction between wood and.tuning pins that are subsequently inserted in the holes of batch ofureaV the pinblock drilled to receive them. The retention of friction isa desirable feature to assist in the tuning of the piano and by thismeans such friction is prolonged for years beyond the point where thepins in the standard construction often become loose, necessitatingtheir removal and the substitution of oversize pins to restore thefriction, or replacement of the entire pinblock because of checking,splitting or warpage.

The advantages of the invention consist in having a waterproofprotective layer that becomes an integral part of the pinblock; inhaving a layer to provide the pinblock with a surface the exactcounterpart of the string f'rame adjacent to it, thereby securing aneiiicient t; reduction in loss of pitch of the strings through warpage,distortion or buckling due to improper or partial t; saving of time inthe tting operation; reduction in the time of curing such iilm by use ofheating by electrostatic field of high frequency; retention of thefriction between wood and tuning pins under climatic changes and theravages of time for prolonged periods due to changes in moisturecontents through atmospheric changes and securing the pinblock againstmoisture entrance.

The filler layer is of such a material that when acted upon as describedit will bond to the Wooden pinblock and register perfectly with thestring frame throughout the entire surface, making the three parts asone tted unit. At the same time, it is important that the treatment ofthe wood is such that it is free from moisture and that it is exteriorlycovered against moisture, so that the wooden pinblock and metal stringframe with the layer therebetween become substantially one moistureproof entity, having at the same time all the advantages of vibrationtranslation due to their intimate chemical and physical bonding.

While pinblocks as heretofore supplied to be manipulated aresubstantially free from moisture when originally supplied, by the timethe fitting operation by trial and error is completed in the normalprocedure described, a certain degree of moisture is absorbed from theair in the shop. It is essential, in accordance with this invention, toexpel such added moisture, and the subsequent heating by electrostaticmeans expels this moisture.

The improved process consists in applying to the upper surface of thepinblock a layer of resin paste in plastic state, impressing the lowersurface of the string frame upon said layer, subjecting the impressedlayer to the action of an electrostatic current to harden the same andcongeal the impressions, subjecting the pinblock to the action of anelectrostatic current to remove the moisture from the body of thepinblock, and enclosing the pinblock by an envelope of water repellantmaterial to prevent the entrance of moisture in the pinblock.

I have described several forms of my invention, but obviously variouschanges may be made in the details disclosed without departing from thespirit of the invention as set out in the following claims,

What I claim is:

l. An improved combined pinblock and string frame, a string frame havingits under surface provided with an irregular surface of projections anddepressions, a pinblock having its upper surface provided with a layerbonded thereto and having the exposed surface of the layer provided withimpressions in complete registration with the contiguous under surfaceof the string frame, without voids or spaces between said contiguoussurfaces, said layer being hard and free from moisture, the pinblockwith its layer being detachably joined to the string frame.

2. An improved combined pinblock and string frame, a string frame havingits under surface provided with an irregular surface of projections anddepressions, a pinblock having its upper surface provided with a layerbonded thereto and having the exposed surface of the layer provided 10with impressions in complete registration with the contiguous undersurface of the string frame, Without voids or spaces between saidcontiguous surfaces, said pinblock being covered throughout all of itsexposed surfaces including the layer bonded thereto with a moisturerepelling coating, the pinblock itself and its layer being free ofmoisture, the pinblock With its layer being detachably joined to thestring frame.

PAUL H. BILHUBER.

